June 04, 2006

First There Was the Grid

3pointD linked to an interesting article on Ogle Earth entitled "Metaverse 2.0" which talks about the fact that Google Earth and Second Life are modeled on the real Earth and a flat Earth, respectively. It argues that SL in particular suffers from a failure of imagination in mapping its world onto a boring, 2D grid and offers both hexagonal, hyperlinked topology and a hyperbolic space as solutions. It is a pretty nice piece and covers a lot of territory that we considered early in SL's history -- back in the "Linden World" days of early 2001 -- so I thought that I'd talk a bit of history as to how we ended up with the 2D grid. Also, I find it interesting that it is completely possible to create the desired world within SL, despite the underlying topological choice.

So where was Linden World in early 2001? At that point we had block-compression working for land transmission, the ability to edge tile simulators, the ability to fly around the world, a spring-membrane water simulation that also crossed region boundaries, and a Jos fluid for the wind. Most of our thoughts at that point were around the combination of a living ecology and cellular automata simulations of various systems, and the topic of overall topology came up quite a bit. Among those that we considered were a grid, a hex-grid, a sphere, a cylinder, a hyperlinked grid, a hyperlinked hex-grid, and even the hyperbolic place talked about in the article. Each of these had strengths and weaknesses.

The simple grid had the advantage of already being done, was conceptually simple, was easy to stick CAs and height fields on top of, and mapped well onto the real terrain that we thought would make up most of Linden World. On the other hand, it isn't very sexy and put sim centers relatively far apart for a given area -- damn Pythagorus! The hyperlinked variant was dismissed because by the time we thought of it quirks in how we managed agents would have made it a pain to handle loops, which is shame because it offers up some interesting features that we'll have to do the hard way via portals and remote cameras.

A hex grid would have been nice for all the same reasons that table top games use them. Edge connected CAs across them would have been slightly more difficult and of course it wasn't actually written yet. In the end, hex grids lost out to a Cartesian grid because we didn't have the resources to tackle problems that weren't absolutely necessary, and the benefits of a non-hyperlinked hex grid over a non-hyperlinked regular grid are marginal. Similarly, the hyperlinked variant is only a bit better than a hyperlinked regular grid. Yes, you get to take one step to 6 neighbors rather than 4, but the regular grid actually gives you 8 neighbors since diagonal moves are allowed, even if it is a slightly longer walk.

The cylinder and spheres were rejected because unlike Google Earth we don't know how big Second Life will actually become and once you start filling in a fixed geometry you have the unfortunate problem of having to either grow the object -- which does work for the Universe, of course -- or having to duplicate it, neither of which seemed like the right option. From a rendering standpoint it might be nice to add some curvature to Second Life, but that is independent of the topology of the land allocation.

The saddle is probably the geekiest option and was suggested to me by a math professor friend at Berkeley. I think it's very cool to see someone else think of it! As mentioned in the article, what's nice about curving a plane onto a saddle is that you get completely different tiling properties, including the option to allow more than 4 squares to meet at a corner -- column 4, row {5,4} I believe. This keeps the world closer together so you can walk to more neighbors easily. The problem is that rendering it in a way that makes sense turned out to be more work than we wanted to try to come up with.

So, that's why we have a 2D grid. But are you really stuck?

In Second Life today you have global teleporting with local, recognizable geometry. I completely agree that we need to make teleporting -- and semantic connections -- easier to create and to use, but they are there. Hell, 2 seconds after we fix llHTTPRequest to use HTTPS I'll have my del.icio.us tracking script posted here, although in the long run we probably don't want to rely on external sites for that sort of tagging. But that aside, you can create nearly all of the desired benefits of the article in Second Life today. In fact, the balance between mainland and island purchases explore those questions and opportunities every day.

Moreover, the question of the value of space and place is a deep one. The web is not a communal place, so hyperlinking may be a better fit than for Second Life. Obviously, we thought so, because from the beginning we sought to create a world that had place. A lot of the impact of that decision is lost in short draw distances, delays on draw-in, and the like, but as we solve those problems, it will be interesting to see how travel breaks down between teleporting and actual travel between places. Teleporting is superior today, but it isn't clear that it is a global maxima. Instead it may simply be a local one created by technological limitations.

Comments

I readily admit the "failure of the imagination" comment is a bit unfair, akin to insisting that version 1.0 be 2.0 or that giants sit on their own shoulders. And I'm a relative neophyte to the genre, so I don't actually know the early history of Second Life, how it evolved, the hard work that must have gone into it.

Great to hear you've considered these options along the way. I'm sure Second Life developers operate under real world resource constraints, even if Second Life doesn't need to:-)

> you can create nearly all of the desired benefits of the article in Second Life today

Okay, Cory, but not the Klein bottle stuff. You can't make a space where you stick to the surface you're walking on no matter how that surface curves. You can't make gravity stick to a wall or a ceiling, or change it on the fly, as in Prey (which also does cool portal stuff).

That's not a criticism, btw, it's just a semantic correction. There's a fairly large subset of envisioned stuff (larger than the inverse of "nearly all") that you can't actually do in SL. It was no doubt a herculean task for you guys just to create what we've got. Now, in SL 2.0, who's to say...

t will be interesting to see how travel breaks down between teleporting and actual travel between places.

The clickthough data on the classifieds yields this information: hardly anybody pulls up the map to see the location's situation in the geographical space. The just p2p there like flipping a page. Once there, they get what they came for, and don't look around for the most part, as anyone can tell you who has put a mall down right smack next to a hugely popular club but not gotten any spillover traffic on the neighbouring sim.

Bringing back the map list with all the names, as much of a draw on resources as it is, could help people's imagination and help them remember names and go places. Right now, most people do not tp using the map.

No, they don't. Watch them and see.

Instead, they either take a friend's TP, or tp on an add with the link built in or a FIND search or most often, they type in the sim's name on the list. That delivers them to the 128/128 mark and they could land in a wall, water, whatever.

The irony of it all is that the private island enclaves got to keep their telehubs and force flying over their more interesting builds to force people to shop at shops around their landing points, but this was seized away from mainlanders, and they were left with bad 128/128 landings.

Huh, Cory, are you on the same web as I am?
The web was never less of a communal space than SL. There are private places in SL and on the web that are mostly deserted, and places where people congregate. SL is about connecting people. You can also chat and play games on the web :)
As for hyperlinking, we already have it, P2P teleport is basically equivalent to it.

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At that point we had block-compression working for land transmission, the ability to edge tile simulators, the ability to fly around the world, a spring-membrane water simulation that also crossed region boundaries, and a Jos fluid for the wind.